Fusion 360 CAM Slot Operation problem



We are going to start producing Covid boxes (COVID Box) for local hospitals in the next couple of days, and I am in charge of running the CNC. Normally this is no big deal (these parts are very simple) but I have run into a problem I have never experienced when using the slot operation. There are 1/4 inch slots that we need to slot out with a 1/4 inch endmill. Should be simple. But when I select the slots I get the following error.


I get this error when I am using both a 1/4 and an 1/8 endmill. After changing all of the parameters nothing changed. Anyone have any ideas?

Screen Record


J Rehagen

At around 30 seconds into the video, it shows your Safe distance. The video’s a bit fuzzy, so I can’t be sure as to what the value is, but it looks to be 0.1xxx in. Safe distance is the distance between the tool and the part during retract moves. Since you’re using a .125" tool in a .25" slot, you only have a maximum of .0625" of clearance around your part at any given time, which could end up causing this error. You could try decreasing this number and it should fix the issue.

Alternatively, I would recommend using a 2D Adaptive Clearing toolpath if your pocket is of bigger width than the tool. You can cut faster and deeper (axially) this way, and it’s better for the tool’s life (although the tool life won’t be affected much at all in polycarbonate).

I changed the safe distance to 0.001 and it did not work.

The Adaptive with an 1/8 inch endmill works, so if we need to we can use that. However, we would prefer using the 1/4 inch endmill on a slot operation because it would be easier and faster (and we wouldnt have to buy more 1/8 enmills - we have one I think). Any more ideas for why it might not work?

Took me a little bit of messing around in fusion to figure this one out, but I think I found the issue. (?) If you zoom in to the middle of the round edge of the slot, you’ll see a flat like this.
image presumably to give .001" clearance so the other lexan sheets can sit in the slot.
Fusion likes its slots to be nice and round, so I cut a slot 2.25" long and .25" wide, and sure enough fusion was fine with it (fusion slot feature defaults to semicircular ends). As far as fixing this goes, I would do 1 of 2 things:

  1. You can get around this by sketching the correct slot .251" wide by 2.25" center to center, then selecting that for your slot operation.
  2. Alternatively, you can make your own “slot” operation by selecting 2D contour, and selecting the same contour you selected for the real slotting operation. You’re gonna wanna change the linear lead in and lead in radius to something really really small (I did .0001"). Just make sure your plunge feedrate is properly set here.

The second will probably be a bit easier, so I’d reccomend that, but the first can work just as well.

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Thank you so much! option 2 worked so I think we will go with that!

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